JP2720681B2 - Mobile object movement detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the movement of a rotating body and the movement of a straight moving body using a magnetoresistive element.

[0002]

2. Description of the Related Art FIG. 8 shows a movement detecting device (rotation sensor) 1.
2 shows an example of detecting the rotation of the motor shaft 2 using the above. In FIG. 1, a gear 3 as an object to be detected is fitted and fixed to a motor shaft 2, and a detection surface of the movement detection device 1 is arranged on a peripheral surface of the gear 3 via a gap.

As shown in FIG. 6, a movement detecting device 1 includes a magnet 5 for generating a bias magnetic field in a case 4.
The upper end surface of the magnet 5 has four magnetoresistive elements MR _A1 , as shown in the circuit diagram of FIG.
MR _A2 , MR _B1 , and MR _B2 are provided, and MR _A1 and M
The magnetoresistive elements of R _A2 are connected in series to form a first phase detection circuit, and the magnetoresistive elements of MR _B1 and MR _B2 are also connected in series to form a second phase detection circuit. ing. The detection circuit of the first phase and the detection circuit of the second phase are connected in parallel, and one end of the parallel connection circuit is connected to the power supply line 6 and the other end is connected to the ground line 7. . The detection signal of the first phase is extracted from the connection between the magnetoresistive elements MR _A1 and MR _A2 , and the detection signal of the second phase is extracted from the connection between the magnetoresistive elements MR _B1 and MR _B2. Have been.

The magneto-resistive elements MR _A1 , MR _A2 , M
R _B1 and MR _B2 are arranged as shown in FIG. That is, the magnetoresistive elements MR _A1 and MR
_{When B1} faces the tooth ridge 3a of the gear 3, the magnetoresistive elements MR _A2 and MR _B2 are arranged so as to face the valley 3b of the tooth of the gear 3, and the pitch of the teeth of the gear 3 is T. , MR _B1 against magnetoresistive element MR _A1 is T / 4, MR _A2 is T /
2, MR _B2 is arranged at a position shifted in phase by 3T / 4. 6 and 7, reference numeral 8 denotes a power supply line 6.
The terminal 8 is connected to a detection circuit of each magneto-resistive element via a lead frame 10.

[0005] By disposing the movement detecting device 1 so as to face the gear 3 and rotating the motor shaft 2, FIG.
As shown in (1), the signal of the first phase detection circuit and the detection signal of the second phase are extracted as a sine waveform signal having a phase difference of T / 4, and by analyzing the voltage of this signal, the motor shaft 2, the rotational movement amount, the rotational speed, and the rotational speed are obtained. The rotation direction of the motor shaft 2 is obtained by extracting the two-phase signals.

[0006]

However, in order to increase the resolution of rotation detection using the conventional movement detecting device 1, it is necessary to use a small module gear having a small pitch T between the teeth of the gear 3. Further, when the gap G between the detection surface of the movement detection device 1 and the gear 3 increases, the sensitivity decreases, so that the gap G also needs to be reduced. However, if the pitch of the gears is reduced by reducing the size of the module of the gear 3, the number of magnetoresistive elements provided between the pitches cannot be increased, and when the pitch of the teeth is reduced, FIG. As shown in the figure, since the detection output decreases, if the detection output is to be increased by that amount, the gap G with the object to be detected must be further reduced. However, if the gap G is too small, it becomes difficult to adjust the position of the movement detection device 1. If the gear 3 is eccentric, there arises a problem that the teeth come into contact with the detection surface of the movement detection device 1. . In order to avoid this, it is difficult to manufacture the gears and to assemble the gears.

In the conventional device, the detection circuit for the magnetoresistive element of each phase is configured to be connected in parallel between the power supply line 6 and the ground line 7, so that the detection circuit for the magnetoresistive element of each phase is used. The applied voltage applied to is increased. Therefore, when the detection circuit of the magnetoresistive element is multi-phased, the power consumption is greatly increased, and a problem arises that the heat generated by the increase in the power adversely affects the detection performance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to enable movement detection with high resolution using an object to be detected such as a gear having a large pitch. An object of the present invention is to provide a movement detection device for a moving body which consumes less power and does not cause a problem of heat generation.

[0009]

The present invention is configured as follows to achieve the above object. That is, the moving body movement detecting device of the present invention comprises four or more elements fixed above the magnetic pole surface of the magnet along the moving direction of the detected part provided at equal pitches on the magnetic body to be detected. Even-numbered magneto-resistive elements are arranged at positions equally dividing the arrangement pitch of the detected parts, and are arranged opposite to the detected body via a gap,
The plurality of magneto-resistive elements are connected in series, and a connection portion between the respective magneto-resistive elements is configured to be a portion for extracting an output signal. A signal processing circuit is provided for performing differential amplification by pairing signals having a phase difference of 周期 cycle among signals extracted from the output signal extraction unit, and outputting the differential amplified output as a detection signal. This is also a characteristic configuration of the present invention.

[0010]

In the present invention having the above-described structure, the movement detecting device is disposed to face the moving body with a gap therebetween, and when the moving body is moved, the detected portion provided on the moving body is shifted depending on the position facing the magnetoresistive element. The line of magnetic force generated by the magnet applying the bias changes, and the magnetic flux density applied to each magnetoresistive element changes. Signals extracted from the output signal extracting section and having a phase difference of 周期 cycle are differentially amplified by a signal processing circuit, and the differential amplified output is output as a movement detection signal of the detection target.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the description of this embodiment, the same parts as those of the conventional example are denoted by the same reference numerals, and the description thereof will not be repeated.
FIG. 1 shows a main configuration of an embodiment of a movement detecting apparatus according to the present invention, and FIG. 2 shows a circuit configuration of the embodiment. The movement detecting device of the present embodiment is also configured using a magnetoresistive element in the same manner as in the conventional example, and this magnetoresistive element is disposed on the upper end surface of the magnet 5 housed in the case 4 as shown in FIG. Has been established.

What is characteristic in this embodiment is that each of the magnetoresistive elements MR1 to MR1
That is, the MRs 8 are connected in series and output signal take-out portions P _{1 to} P ₇ are provided at respective series connection portions. As shown in FIG. 3, the eight magneto-resistive elements MR1 to MR8 are connected to the four magneto-resistive elements MR1 to MR
When R4 is opposed to the peak 3a of the teeth, the remaining magnetoresistive elements MR5 to MR8 are arranged to be opposed to the valley 3b of the gear 3. When the pitch of the teeth of the gear 3 is T, each magnetoresistive element MR1 ＭＲMR8 are arranged at intervals of T / 8.
Each magnetoresistive element MR1~MR8, by the gear 3 as the detected body rotates, the output signal of the sine wave is outputted from the take-out portion P ₁ to P ₇ of each signal.

[0013] In other words, the applied voltage of the power supply line 6 V _in
Of time, the output signal of the extraction portion P ₁ of the signal (7R-r
sin θ) V _in / 8R, and the output signal from the P ₂ {6
R− (2 + 2 ^1/2 ) ^1/2 rsin (θ + π / 8)｝ V _in /
8R, and the output signal of the P ₃ is {5R- (1 + 2 ^1/2)
rsin (θ-π / 4) } V in / 8R , and the output signal of the P ₄ is {4R- (4 + 2 × 2 1/2) 1/2 rsin (θ-3
_{π / 8)} V in /} 8R , and the output signal of P ₅ is {3R
^{- (1 + 2 1/2) rsin} (θ-π / 2)} V in / 8R , and the output signal of the P ₆ are ^{{2R- (2 + 2 1/2)} rsin
(Θ-5π / 8)} V in / 8R , and the output signal of the P ₇ becomes {R-rsin (θ-3π / 4)} V in / 8R.
In these equations, R is the center value of the resistance change of each magnetoresistive element, r is the fluctuation value of the same resistance change, θ is the amount of rotational movement of the gear 3, and has a relationship of 2π = T.

As can be seen from the above equation, the output signal P ₁
And P ₅ are signals having a phase shifted by T / 2, that is, 180 °, and similarly, P ₂ and P ₆ , and P ₃ and P ₇ respectively have T / 2.
Phase signal is to become a pair mutually shifted by, as shown in the signal of each pair 2, are differentially amplified by the differential amplifier circuit 12 of the signal processing circuit 11, P ₄ is passing a buffer amplifier in the output E ₁ to E ₄ it is outputted as a detection signal of the object to be detected. Each detection signal E ₁ ~E ₄ is V _in
/ 2, and becomes a sine waveform signal having an amplitude and a period of (4 + 2 × 2 ^1/2 ) ^1/2 rcos θ, and these detection signals E _{1 to} E ₄ are out of phase by π / 8. When the gear 3 of the object to be detected is rotated, the amount of rotation, the rotation speed, and the number of rotations of the gear 3 are obtained as a detection signal E _1.
And thus it obtained by analysis of the to E _4.

In this embodiment, since the magnetoresistive elements MR1 to MR8 are connected in series between the power supply line 6 and the ground line 7, each of the magnetoresistive elements MR1 to MR8 is connected.
Voltage applied becomes very small compared with the conventional example, the current consumption in this embodiment is next V _in / 8R, compared to 4V _in / 2R in the conventional example of the device, next to 1/16, thereby, the It is possible to significantly reduce power consumption. In addition, by increasing the number of phases, that is, the number of magnetoresistive elements, this ratio is further reduced, and power consumption can be further reduced. This reduction in power consumption also eliminates the problem of adverse effects on performance due to heat generation of each of the magnetoresistive elements MR1 to MR8.

Further, since the power consumption is reduced, the size of the magneto-resistive elements MR1 to MR8 can be further reduced. As a result, the number of the magneto-resistive elements can be increased to increase the arrangement density. An object to be detected with high resolution can be detected.

Further, as described above, the magnetoresistive element MR1
Since the current consumption of the MR8 is reduced, the pitch of the object to be detected, that is, the pitch of the gear 3 in this example is increased, that is, a large gear of the module can be used, as shown in FIG. As a result, the output of the detection signal increases, and accordingly, the gap G with the object to be detected can be increased. Therefore, it is not necessary to pay close attention to the eccentricity and the like of the gear 3, and the mounting and adjustment of the movement detecting device 1 becomes easy, and the structure of the mounting device can be simplified. In addition, as the size of the gear 3 is increased, there is an advantage that the number of magnetoresistive elements arranged in one pitch can be further increased.

The present invention is not limited to the above embodiment, but can take various embodiments. For example, in the above embodiment, the gear 3 was used as the object to be detected. However, the object to be detected may be a linear non-magnetic material scale provided with magnetic materials as detection portions at equal pitch intervals on the scale, or a magnetic material. The linear scale may be magnetized at equal pitch intervals, and the magnetized portion may be used as a portion to be detected. By using these linear scales, for example, the feed movement of a bet or the like of a machine tool may be performed. Detection can be performed similarly.

In the above embodiment, the magnetoresistive element is 8
Although the number of the magnetoresistive elements has been described, the number of the magnetoresistive elements is not limited as long as the number is four or more.

Further, a signal processing circuit 11 including a plurality of differential amplifiers 12 for processing the output signals P _{1 to} P ₇ from the respective signal extraction units and resistors R 1 to R 9 is disposed in the case 4 of the apparatus. Alternatively, it may be arranged outside the case 4.

[0021]

According to the present invention, four or more magnetoresistive elements for detecting a portion to be detected of an object to be detected are connected in series, and an output signal is taken out from each connection portion. Power consumption for operation can be reduced, power consumption can be reduced, and the problem of heat generation of the magnetoresistive element can be eliminated.

Further, for example, in the case of detecting rotation movement using a gear, the pitch of the detected portion, that is, the pitch of the gear can be increased, so that the output of the detection signal increases, and the output of the detection signal increases accordingly. Since the gap between the object to be detected and the object to be detected can be increased, it is very easy to adjust the position between the object to be detected and the movement detecting device and to mount the movement detecting device.

Further, as described above, the arrangement pitch of the detection target portion of the detection target such as a gear can be increased and the power consumption can be reduced, so that the number of arrangements of the magnetoresistive elements can be increased accordingly. Thus, the movement of the detected object can be detected finely, and the reliability of the movement detection of the moving object can be enhanced.

Further, by connecting the magnetoresistive elements in series, the number of detection signals to be extracted is increased as compared with the conventional example, which is very advantageous in signal processing.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing one embodiment of a moving body movement detecting device according to the present invention.

FIG. 2 is a circuit configuration diagram in the embodiment.

FIG. 3 is an explanatory diagram showing an arrangement of a magnetoresistive element in the embodiment in relation to a gear of a detection target.

FIG. 4 is a graph showing the relationship between the tooth pitch of a gear and the level of a detection signal when the gear is the object to be detected.

FIG. 5 is an explanatory diagram showing an arrangement of a magnetoresistive element in a conventional example in relation to a gear of an object to be detected.

FIG. 6 is an explanatory diagram of a general structure of a movement detection device of a moving body.

FIG. 7 is a circuit diagram of a conventional moving object detection device using a magnetoresistive element.

FIG. 8 is an explanatory diagram of a state in which a rotational movement of a motor shaft is detected using a gear as a detection target.

FIG. 9 is a graph of an example of detection of rotational movement in the state of FIG. 8;

[Explanation of symbols]

1 movement detecting device 11 signal processing circuit 12 a differential amplifier circuit _{MR A1, MR A2, MR B1} , MR B2, extraction of MR1~MR8 magnetoresistive element P ₁ to P ₇ output signals E ₁ to E ₄ detection signal

Claims (2)

(57) [Claims] 1. An even number of four or more magnetoresistive elements fixed above a pole face of a magnet along a moving direction of a detection part provided at equal pitches on a magnetic detection target. The plurality of magneto-resistive elements are arranged at positions that equally divide the arrangement pitch of the detection units, are opposed to the object to be detected, with a gap therebetween, and the plurality of magneto-resistive elements are connected in series. A movement detection device for a moving body serving as a take-out unit. 2. Among the signals extracted from each output signal extraction section, differential amplification is performed by pairing signals having a phase difference of 1/2 cycle as a pair, and the differential amplification output is output as a detection signal. The moving object detection device according to claim 1, further comprising a signal processing circuit.